Abstract:

The Renzidong Cave site is one of the oldest Paleolithic localities in East Asia. During the excavation as part of the State Key Project of the Ninth Five-Year Plan, numerous stone and bone artifacts were discovered during 1998 to 2005. In addition, abundant vertebrate fossils were also yielded. All four Quaternary perissodacty l families (Equidae, Rhinocerotidae, Tapiridae, and Chalicotheriidae) have been reported, including Hesperotherium huaiheense. From 2020 to 2024, a joint team from the Institute of Vertebrate Paleontology and Paleoanthropology (Chinese Academy of Sciences) and the People’s Government of Fanchang District, Wuhu City, conducted a second round of excavations at the Renzidong Site. Several well-preserved teeth of Chalicotheriidae were collected. Quaternary chalicotheres represent a relict Neogene lineage and were among the first fossil vertebrates reported from China. After decades of debate and revision, most Quaternary chalicothere specimens had been as assigned to Hesperotherium sinense. The known distribution of H. huaiheense is limited to the Renzidong site. The new chalicothere specimens from Renzidong are much better preserved than the type specimens and exhibit a moderate degree of wear, thereby retaining important morphological characters. The new molars exhibit a reduced posterior part of the metacone and a distinctly trapezoidal occlusal outline of M3 with a constricted posterior part; the lingual cingulum is absent at the opening of the central valley of M3. All of these features are identical to those of H. huaiheense but differ from typical H. sinense. Some authors once regarded H. huaiheense as a subspecies of H. sinense based on the view that all morphological differences fall within the variation of H. sinense. We interpret the reduced metacone and absent lingual cingulum as having evolutionary and ecological significance, respectively. We therefore recognize H. huaiheense as a valid species. Another subspecies, H. sinense primigenius, retains primitive characters (e.g., a remnant protoloph), which also have evolutionary significance. Hesperotherium had a long temporal range spanning much of the Early Pleistocene (from 2.6 Ma to 1.0 Ma). Recognizing multiple species within this genus is a reasonable approach, although it depends on further discovery and research. Morphological similarities between Hesperotherium and the South American Megatherium suggest analogous ecological adaptations. Recent paleoecologic analyses indicate that both genera likely occupied similar habitats.

Key words: Fanchang, Anhui, Renzidong Cave site, Hesperotherium huaiheense, early Early Pleistocene, Palaeoecology